Chemical mechanical polishing (CMP) of copper in ammonium hydroxide based slurry in the presence of hydrogen peroxide was investigated. The polishing trend was found to be similar to that exhibited by other slurries containing hydrogen peroxide and various complexing agents used for Cu CMP. When the hydrogen peroxide concentration is increased, the polish rate increases, reaches a maximum and then decreases. The location and the magnitude of the maximum depend on the ammonium hydroxide concentration. The dissolution of copper in the NH4OH-hydrogen peroxide solution was probed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) experiments. Electrical equivalent circuit (EEC) and reaction mechanism analysis (RMA) were employed to determine the mechanistic reaction pathway of Cu dissolution in NH4OH-hydrogen peroxide system. Based on the RMA analysis, a four step catalytic mechanism with two adsorbed intermediate species is proposed. © 2009 Springer Science+Business Media B.V.

Srinivasan Ramanathan

Department Of Chemical Engineering

ADSORBED INTERMEDIATES

ammonium hydroxide

Catalytic mechanisms

COMPLEXING AGENTS

Electrical equivalent circuit

Electrochemical characterizations

HYDROGEN PEROXIDE CONCENTRATION

POLISH RATE

REACTION MECHANISM ANALYSIS

Reaction pathways

AMMONIUM COMPOUNDS

CHEMICAL POLISHING

Copper

dissolution

Electric network analysis

Electrochemical corrosion

Electrochemical impedance spectroscopy

Hydrogen

Hydrogen peroxide

oxidation

Polishing

Slurries

CHEMICAL MECHANICAL POLISHING

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Applied Electrochemistry

The cleaning of copper surface after chemical mechanical planarization (CMP) process is a critical step since the surface would be contaminated by a large number of slurry particles such as silica or alumina and organic residues such as benzo triazole (BTA). The presence of organic residues results in a hydrophobic surface, which leads to problems in particle removal and drying. A major function of a post copper CMP cleaning solution is to remove these organic contaminants without significant increase in the surface roughness. Alkaline or acidic cleaning solutions are usually preferred over neutral solutions since they can remove organic residues better. The objective of this work is to formulate an alkaline cleaning solution and characterize its efficiency on particle and BTA removal. The cleaning solution studied consists of tetra methyl ammonium hydroxide (TMAH) as the cleaning agent and arginine as the chelating agent. The removal of BTA is characterized using contact angle measurements and electrochemical techniques. The proposed cleaning solution showed good ability in removing BTA and silica particles from the copper surface and also yielded a lower surface roughness. Arginine facilitates complexing of Cu ions thereby preventing redeposition. © 2011 Elsevier B.V. All rights reserved.

Microelectronic Engineering

Characterization of TMAH based cleaning solution for post Cu-CMP application

The effect of l-glutamic acid as complexing agent in the presence of hydrogen peroxide as oxidizer in copper chemical mechanical polishing (CMP) slurry is investigated. In the CMP process, the work surface is moved against a pad, with slurry flowing between the surface and the pad. The polish rate was found to be stable over a wide range of hydrogen peroxide concentration. High concentration of either l-glutamic acid or hydrogen peroxide leads to a reduction in polish rate, but a high concentration of both chemicals does not reduce the polish rate. In the absence of hydrogen peroxide, the Cu polish rate was 0 for all the l-glutamic acid concentrations investigated. However, potentiodynamic polarization curves do not show any sign of passivation when l-glutamic acid was present in the solution. In situ open circuit potential measurements show that copper redox reactions as well as hydrogen peroxide redox reactions contribute in determining the electrochemical behavior. We propose that l-glutamic acid inhibits the copper dissolution by adsorption onto the metallic copper, but enhances copper dissolution by complexing copper ions. The results show that it is possible to conduct controllable copper CMP in mildly acidic slurries with hydrogen peroxide as oxidizer and l-glutamic acid as complexing agent. © 2010 Springer-Verlag.

Journal of Solid State Electrochemistry

Electrochemical characterization of copper chemical mechanical polishing in l-glutamic acid-hydrogen peroxide-based slurries

The dissolution of copper in solutions containing Glutamic acid and hydrogen peroxide is analyzed using EIS. Potentiodynamic polarization studies show that there is no strong passivating layer formed on the copper surface in solutions containing 0.5 wt% Glu and 0.1 vol% hydrogen peroxide. Electrochemical impedance spectra of copper in this solution at various overpotential were acquired and modeled using electrical equivalent circuit and reaction mechanism analysis. The results show that the reaction involves at least two adsorbed intermediates. ©The Electrochemical Society.

ECS Transactions

Analysis of copper dissolution in glutamic acid and hydrogen peroxide using EIS

Anodic dissolution of copper in arginine and hydrogen peroxide-based medium suitable for chemical mechanical planarization slurry formulation was investigated using electrochemical impedance spectroscopy. Potentiodynamic polarization and impedance data were acquired for copper dissolving in hydrogen peroxide and arginine solution. Reaction mechanism analysis (RMA) was employed to determine the mechanistic pathway of copper dissolution. RMA analysis indicates that a stable passivating film does not form on the copper surface, and the direct dissolution of copper was also ruled out. A two-step mechanism involving cupric oxide as an intermediate species is proposed. The data were also fit to an electrical equivalent circuit to obtain insight into the variation of the parameters with the overpotential. The modeled data for the two-step mechanism captures the essential features of the impedance spectra at various overpotentials. © 2008 Springer-Verlag.

Fulltext

Electrochemical impedance spectroscopic studies of copper dissolution in arginine-hydrogen peroxide solutions

Chemical mechanical planarization of copper disks in hydrogen peroxide and l-arginine based alkaline slurry was investigated. Various commonly proposed inhibitors were screened by static etch rate experiments and only BTA and uric acid were found to be effective in the alkaline pH range, while potassium sorbate was moderately effective. The combination of arginine, hydrogen peroxide and uric acid leads to a more robust polish rate than can be achieved with glycine, hydrogen peroxide and BTA based slurries. The dissolution in presence of uric acid was further studied by potentiodynamic and cyclic polarization experiments which indicate formation of a passivation layer on the copper surface. Silicon dioxide wafers were polished to determine the Cu/silicon dioxide polish rate selectivity in alkaline pH range and a high selectivity (>100) was observed. These results indicate that it is possible to conduct a robust copper CMP with alkaline slurries while maintaining an excellent Cu/silicon dioxide polish rate selectivity. © 2007 Elsevier Ltd. All rights reserved.

Electrochimica Acta

Chemical mechanical planarization of copper in alkaline slurry with uric acid as inhibitor

Materials Chemistry and Physics

Chemical mechanical planarization of copper using abrasive-free solutions of oxalic acid and hydrogen peroxide

Journal of The Electrochemical Society

An Impedance Investigation of the Mechanism of Pure Magnesium Corrosion in Sodium Sulfate Solutions

Anodic Dissolution of Nickel across Two Consecutive Electron Transfers

Electrochemical characterization of Cu dissolution and chemical mechanical polishing in ammonium hydroxide-hydrogen peroxide based slurries

Journal	Journal of Applied Electrochemistry
ISSN	0021891X
Open Access	No